Expression of α-Methylacyl-CoA Racemase (P504S) in Nephrogenic Adenoma: A Significant Immunohistochemical Pitfall Compounding the Differential Diagnosis With Prostatic Adenocarcinoma

Müllerianosis of the urinary bladder may simulate a bladder cancer: a case report

Müllerianosis is an extremely rare entity consisting of an admixture of 2 or more müllerian tissues. We report the case of a 61 years old woman who came to our attention with hypogastric pain and dysuria. She was in menopause and had a previous history of cesarean section. Ultrasound and CT-scan of the abdomen showed a proliferative bladder lesion close to the left ureteric orifice. Transurethral resection of the bladder (TUR-B) was performed. Histopathological examination of the specimens was negative for bladder cancer and revealed the presence of endosalpingeal tissue. Postoperative course was unremarkable as well as follow up at 12 months. A proper knowledge and awareness of this disease, even if rare, is necessary for an accurate differential diagnosis and to perform an appropriate treatment. (www.actabiomedica.it)

Tumour-like lesions of the urinary bladder

There are a number of benign epithelial proliferations in the bladder that may be difficult to distinguish from carcinomas, including urothelial carcinoma and its variants, squamous cell carcinoma and adenocarcinoma. If misdiagnosed, there is the potential for over treatment, with its attendant risk of complications, as well as errors relating to prognostic assessment. In the case of the misdiagnosis of high grade proliferative lesions that mimic invasive carcinoma, unnecessary radical surgery, chemotherapy and radiotherapy may result. Similarly, the misdiagnosis of lesions that have the appearance of low grade carcinoma can prompt a lifetime of radiological investigation and cystoscopies. In this review, we discuss a variety of entities that may be diagnostically challenging and emphasise the importance of identifying key morphological features that have diagnostic utility. We also highlight the importance of relevant clinical information and the clinical settings in which these lesions may occur. In this review we have divided the lesions on the basis of morphology in order to facilitate discussion relating to the differential diagnosis. The architectural patterns we discuss include papillary lesions (polypoid/papillary cystitis and papillary urothelial hyperplasia), pseudocarcinomatous proliferations (pseudocarcinomatous urothelial hyperplasia, florid proliferation of von Brunn nests and fibroepithelial polyps), glandular lesions (intestinal metaplasia and müllerianosis) and lesions with several different patterns (prostatic type urethral polyps and nephrogenic adenoma or metaplasia).

The auxiliary diagnostic value of prostate-specific antigen and α-methylacyl-CoA racemase in prostate cancer

Prostate cancer (PCa) is one of the most common types of malignant tumor, which places a major burden on the health of men, worldwide. A prerequisite to ensure good treatment outcomes for patients with PCa is an accurate diagnosis. The present study aimed to investigate the diagnostic value of prostate-specific antigen (PSA) and α-methylacyl-CoA racemase (P504S) in PCa, using the tumor-associated immunolabels. In total, clinical data was collected from 125 patients undergoing prostate biopsy or surgery between January 2015 and September 2019, and stratified into: PCa (45), benign prostatic hyperplasia (BPH) (60) and unconfirmed diagnosis (20). Immunohistochemistry analysis was performed to assess PSA and P504S expression levels in each group compared with that in the controls (the normal tissue in each group was the internal control). The results demonstrated that the expression level of P504S was significantly higher in the PCa group compared with that in the BPH group. Furthermore, no significant association was observed in the PCa group between PSA and P504S expression levels, and the Gleason grading groups. A total of 20 unconfirmed diagnoses was verified via PSA/P504S. Taken together, the results suggest that combination PSA and P504S have a positive effect in identifying prostate cancer. However, PSA and P504S still have limitations in their diagnosis and the final results need to be carefully and comprehensively analyzed, thus further studies are required to determine their diagnostic values.

[Verumontanum mucosal hyperplasia as a differential diagnosis of a local recurrence following radical prostatectomy]

Verumontanum mucosal gland hyperplasia (VMGH) is a benign microacinar proliferative lesion, which occurs exclusively in the verumontanum and the posterior urethra and is one of the lesions that may be confused with a low-risk adenocarcinoma of the prostate gland.We present the case of a 72-year-old male patient who underwent radical prostatectomy due to an adenocarcinoma of the prostate gland (pT2c pN0 cM0 R0, Gleason Score: 3 + 3 = 6). Five years after the operation, we sonographically detected a 3x2 cm large tumour in the prostate bed. While our first assumption was a PSA-negative local recurrence following radical prostatectomy, a comprehensive histological examination along with the clinical evaluation led us to the diagnosis of a VMGH. VMGH is a less well-known differential diagnosis of PSA-negative local recurrence following radical prostatectomy, whose clinical manifestation should be presented.

Immunohistochemical Pitfalls in Genitourinary Pathology: 2018 Update

Immunohistochemistry may be a very useful adjunct to morphologic diagnosis in many areas of surgical pathology, including genitourinary pathology. In this review, we address common diagnostic dilemmas where immunophenotypic analysis may be utilized and we highlight pitfalls specific to each scenario. For prostate, we review the diagnosis of limited prostatic adenocarcinoma and the distinction of high-grade prostatic adenocarcinoma from urothelial carcinoma. We also cover markers of urothelial lineage in the diagnosis of metastatic carcinoma of unknown primary site. In the kidney, distinction of poorly differentiated renal cell carcinoma from urothelial carcinoma and epithelioid angiomyolipoma, adjuncts to the recognition of hereditary renal neoplasia, and the diagnosis of metastatic renal cell carcinoma are discussed. Finally, for testis we address distinction of germ cell tumors from sex cord-stromal tumors, as well as the diagnosis of metastatic germ cell tumors.

Benign mimics of prostatic adenocarcinoma

Benign mimics present either as common challenges in daily routine practice or may cause diagnostic dilemmas because some are less commonly seen and one may be less familiar in recognizing them. There are a multitude of mimics of prostatic adenocarcinoma, which may represent normal gland structures, benign proliferations, atrophic lesions, hyperplastic or metaplastic changes, and inflammatory processes. Some of them are preferentially found in certain anatomic areas of the prostate, either confined to the prostate, or outside of the gland. Various benign mimics of prostatic carcinoma may be also evaluated based on their morphologic similarity to Gleason patterns 3-5 of prostatic adenocarcinoma. Most of the mimics are easily recognizable in larger specimens, such as TUR of the prostate or radical prostatectomy specimens, but they may pose diagnostic problems when the evaluation is done on limited tissue, such as needle-core biopsies or if prostate specimens are infrequently encountered in practice. Therefore, before signing out a report with a diagnosis of prostatic carcinoma, pathologists should carefully consider and rule out the various benign lesions that may mimic carcinoma. This is particularly relevant in the current prostate biopsy practice which relies on using extended biopsy core templates. The awareness and familiarity with the characteristic features of the mimics and judicial use of additional ancillary tests, including immunohistochemistry can prevent overdiagnosis and false-positive interpretation. This review provides a contemporary update on the broad spectrum of the benign prostatic lesions that can mimic prostate adenocarcinoma, outlines their key morphologic and immunohistochemical diagnostic features, and provides a diagnostic, pattern-based approach in establishing a correct diagnosis and distinguishing them reliably from prostatic adenocarcinoma.

Typing the atypical: Diagnostic issues and predictive markers in suspicious prostate lesions

As much as 5% of prostate biopsies yield findings equivocal for malignancy even for skilled uropathologist; such "grey zone" lesions have been addressed in many ways, although the acronym ASAP (atypical small acinar proliferation) is the most widely used when referring to an atypical focus suspicious, but not diagnostic, for malignancy. Since the introduction of this diagnostic category more than 20 years ago, debate has ensued over its histological characterization and clinical significance. Pathology reporting of ASAP, commonly based on strict morphological criteria and traditional immunohistochemical markers such as basal cell antibodies, has been improved by recent availability of novel immunohistochemical markers such as AMACR and ERG. Further pathological issues, such as the role of pre-analytical variables, number of tissue levels, interobserver variability, and association with prostatic intraepithelial neoplasia also play a role in the optimal assessment of ASAP. Apart from diagnostic issues, a major issue is ASAP predictive value for prostate cancer on repeat biopsy. Therefore, attempts have been made to identify clinical and biological parameters that could predict subsequent diagnosis of malignancy as well as define time and modality of repeat biopsy. Finally, pathological features of cancers detected after a previous ASAP diagnosis are compared with those diagnosed at first prostate biopsy.

Nephrogenic adenoma in elderly patients: Three case reports

Nephrogenic adenoma (NA), referred to as nephrogenic metaplasia, is a rare benign lesion of the urinary tract. NA is histologically characterized by tubular and papillary formations lined by low cuboidal to columnar epithelial cells. NA is also immunohistochemically characterized by positivity for paired box (PAX) 2, PAX8 and cytokeratin 7, and negative for p63 and prostate-specific antigen. In this study, we present 3 cases of NA arising in the urinary bladder of elderly male patients with predisposing factors: patient 1 had undergone transurethral lithotripsy due to a ureteral stone; patient 2 had undergone transurethral resection of a urothelial carcinoma in the urinary bladder; and patient 3 had been treated with Bacillus-Calmettle-Guérin due to a urothelial carcinoma in the urinary bladder. The characteristics of the NAs of our 3 cases were histologically and immunohistologically consistent with previously reported cases, although 1 patient exhibited a pseudoinvasive pattern. Since NA is a tumor-like benign lesion, it should be clearly differentiated morphologically and immunohistologically from other tumors arising in the urinary tract and from invasion by prostate cancer.

Nephrogenic Adenoma of the Urinary Bladder: A Review of the Literature

Background. Nephrogenic adenoma of the urinary bladder (NAUB) is a rare lesion associated with nonspecific symptoms and could inadvertently be misdiagnosed. Aim. To review the literature. Methods. Various internet search engines were used. Results. NAUB is a benign tubular and papillary lesion of the bladder, is more common in men and adults, and has been associated with chronic inflammation/irritation, previous bladder surgery, diverticula, renal transplantation, and intravesical BCG; recurrences and malignant transformations have been reported. Differential diagnoses include clear cell adenocarcinoma, endocervicosis, papillary urothelial carcinoma, prostatic adenocarcinoma of bladder, and nested variant of urothelial carcinoma; most NAUBs have both surface papillary and submucosal tubular components; both the papillae and tubules tend to be lined by a single layer of mitotically inactive bland cells which have pale to clear cytoplasm. Diagnosis may be established by using immunohistochemistry (positive staining with racemase; PAX2; keratins stain positive with fibromyxoid variant), electron microscopy, DNA analysis, and cytological studies. Treatment. Endoscopic resection is the treatment but recurrences including sporadic malignant transformation have been reported. Conclusions. There is no consensus on best treatment. A multicentre study is required to identify the treatment that would reduce the recurrence rate, taking into consideration that intravesical BCG is associated with NAUB.

The Application of Immunohistochemical Biomarkers in Urologic Surgical Pathology

Context

Tumors of the genitourinary tract can be diagnostically challenging, particularly in core biopsies and cystoscopic biopsies with limited material. Immunohistochemistry is a valuable tool to use when morphology alone is insufficient for diagnosis.

Objectives

To review tumors and benign lesions of the kidney, urinary bladder, prostate gland, testis, and paratesticular structures with an emphasis on difficult differential diagnoses, as well as staining patterns in normal tissue. Recommended immunohistochemical stain panels are discussed that can assist in the diagnostic workup.

Data Sources

Review of current literature.

Conclusions

Immunohistochemistry is a valuable tool, assisting in the diagnosis of problematic tumors and benign lesions of the genitourinary tract.

Müllerianosis of the Urinary Bladder: A Rare Tumorlike Lesion

Müllerianosis was first described as a rare entity consisting of an admixture of cervical, tubaric, or endometrial epithelium within the lamina propria and muscularis propria of the urinary bladder. This lesion occurs mainly in the dome or posterior wall of the urinary bladder in women of fertile age. Its clinical presentation is characterized by hematuria, pelvic pain, and dysuria, nonspecific symptoms that are related to the responsiveness of müllerian glands to hormonal stimuli. The major interest of müllerianosis resides in its similarity, from clinical, cytologic, and histologic viewpoints, to more threatening conditions, such as neoplasias. The clinical context and the identification of periglandular endometrial stroma at histologic examination with conventional hematoxylin-eosin stain, as well as the immunohistochemical demonstration of estrogen and progesterone receptors in the glands, are of diagnostic utility in the differential diagnosis. Müllerianosis may be responsive to gonadotropin-releasing hormone agonists. Surgical resection may be justified in the case of clinical symptoms refractory to hormone therapy.

Nephrogenic adenoma of the urinary tract: clinical, histological, and immunohistochemical characteristics

Nephrogenic adenoma is a benign condition of the urinary tract resulting from the displacement and seeding of renal tubular cells from the renal pelvis to the urethra. A retrospective series of 134 cases collected from four hospitals in three different countries was analyzed in this study. Recorded clinical data included age and sex, topography, urological antecedents, coexistent lesions, and follow-up. Cytonuclear and architectural features were reviewed, and PAX-8, p63, PSMA, S100A1, CEA, EMA, CD117, cannabinoid receptor CB1, AMACR, E-cadherin, and CD10 antibodies were included in an immunohistochemical panel. Males predominated (105 M/29 F) with an average age of 66 years (range, 14-96). Urothelial carcinoma was the most frequent clinical antecedent (43.2 %) and also the most common coexisting lesion (14 %). Tubular architecture was the most frequent pattern detected (40 %) although most cases showed a mixed pattern (45.5 %). Deep infiltrative growth into the muscularis propria occurred in two cases. EMA and PAX-8 were expressed in 100 % of nephrogenic adenomas, while E-cadherin reactivity was observed in 66.6 % of cases, cannabinoid receptor CB1 in 25 %, CD10 in 13.6 %, CD117 in 4.1 %, and AMACR in 2.7 %. For the rest of the antigens, no reactivity was found. The average time lapse between the pathological antecedent and the discovery of a nephrogenic adenoma was 32 months. We conclude that nephrogenic adenoma displays a broad spectrum of histological features that may mimic malignancy. In our experience, CB1 immunostaining adds a further argument in favor of a renal origin of this lesion. The combination of PAX-8+, p63-, and EMA + distinguishes nephrogenic adenoma from urothelial and prostate carcinoma, its most frequent malignant look-alikes.

Clinical implications of current developments in genitourinary pathology

CONTEXT

Several developments in genitourinary pathology are likely to change our understanding and management of some genitourinary cancers considerably.

OBJECTIVE

To review 5 stories in genitourinary pathology: (1) fusion in the ETS (E26) gene family in prostatic adenocarcinoma; (2) insulin-like growth factor II messenger RNA-binding protein 3 (IMP3), an important prognostic biomarker for kidney and bladder cancers; (3) translocation renal cell carcinoma; (4) UroVysion fluorescence in situ hybridization test in urine cytology for detection of bladder cancer; and (5) the use of triple immunostaining for diagnosis of prostate cancer.

DATA SOURCES

Literature review and authors' personal experiences.

CONCLUSIONS

Many scientific findings have contributed recently to the understanding of the natural pathogenesis and progression of genitourinary cancers. This translational research helps in diagnosing, predicting, and potentially, treating genitourinary cancers.

Flat pattern of nephrogenic adenoma: previously unrecognized pattern unveiled using PAX2 and PAX8 immunohistochemistry

Nephrogenic adenoma is a benign lesion of the urinary tract, particularly the urinary bladder. It is a gross and microscopic mimicker of urothelial neoplasm or metastatic carcinoma. Several histological patterns (tubular, tubulocystic, polypoid, papillary, fibromyxoid) have been recognized, but a flat pattern has not been described. Histologically, nephrogenic adenoma consists of tubules, cysts or papillae lined by flat to polygonal cells with frequent hobnail appearance. The stroma is often edematous or has a granulation tissue-like appearance with acute or chronic inflammation. By immunohistochemistry, nephrogenic adenomas are positive for renal epithelial markers CK7, CD10 and alpha-methylacyl-coenzyme A racemase, and negative for bladder urothelium or prostate markers. Recent studies have shown that nephrogenic adenomas are positive for PAX2 and PAX8. We encountered an interesting case of tubular nephrogenic adenoma with adjacent areas suspicious of flat urothelial atypia. Immunohistochemistry for PAX2 and PAX8 were positive in these areas, unveiling a flat pattern of nephrogenic adenoma. This case prompted us to study 15 cases of nephrogenic adenoma to determine additional instances of flat pattern and to assess the value of PAX2 and PAX8 immunoreactivity to diagnose nephrogenic adenoma. PAX2 and PAX8 immunostaining was positive in 14/15 and 15/15 cases, respectively. The flat pattern was present at least focally adjacent to tubular, polypoid and papillary areas, in 8/15 cases of nephrogenic adenoma. In conclusion, the flat pattern is a common finding in nephrogenic adenomas, but easily under recognized by morphologic examination and may be confused with flat urothelial lesions with atypia. Immunostains for PAX2 and PAX8 are useful in the detection of nephrogenic adenomas and particularly unveil those nephrogenic adenomas with flat pattern.

Nephrogenic adenoma: an immunohistochemical analysis using biotin-free methods

Nephrogenic adenoma (NA) has been considered as a metaplastic process of the urothelium. It has been suggested that this lesion is of renal tubular cell origin or differentiation. Immunohistochemical studies of NA emphasize its staining with α-methylacyl-coenzyme A racemase (AMACR), and prostatic adenocarcinoma may be a possible differential diagnosis. This reactivity was recently discussed as an artifact due to endogenous biotin. Kidney-specific cadherin (Ksp-cad) is a marker of distal nephron. CD10 and KIT are also expressed in the kidney. We studied the immunohistochemical expression of AMACR, p63, Ksp-cad, CD10, and KIT in 9 cases of NA (forming a total of 12 lesions). Practically all of the lesions stained for AMACR with 2 different antibodies and 2 high-sensitivity (multimer or polymer based) biotin-free methods (83% and 100%). The staining was similar for both methods in 9 of these 12 lesions. All of the NAs were negative for p63 and KIT, except 1 case, with focal reactivity for KIT. CD10 was expressed very focally in 4 of the 12 lesions (33%). We observed weak staining for Ksp-cad in 6 lesions (50%) and 3 (25%) showed a moderate positivity in 15% to 50% of the cells. In conclusion, positivity of NA for AMACR is not an artifact, as we confirmed using 2 different methods. Besides, p63, a basal cell marker, is usually negative. Immunoreactivity for Ksp-cad seems to support the differentiation of NA to distal nephron cells, at least in some of the cases. Other markers expressed by the nephron, such as CD10 and KIT, are usually negative in NA.

Nephrogenic Adenoma of the Urinary Tract

Nephrogenic adenoma (NA) is an uncommon and intriguing lesion in the urinary tract. The pathogenesis of NA is not entirely clear. NA was considered to be a metaplastic process of the urothelium in response to chronic irritation of the urinary tract. However, recent evidence has shown that NA is not a metaplastic lesion but rather a proliferation of exfoliated and implanted renal epithelial cells in the urinary tract. Histologically, NAs exhibit, singly or in combination, tubules, small papillae, and microcystic structures lined by cells with little cytological atypia and focal hobnail changes. Solid formations and compressed spindled cells within a fibromyxoid background are rarely observed. Differential diagnosis includes, but is not limited to, malignant neoplasms occurring at the same sites, in particular urothelial carcinoma with deceptively bland morphology (with small tubules, microcystic and nested variants), prostatic adenocarcinoma, and clear cell adenocarcinoma. Immunohistochemical studies with antibodies targeting members of the paired box gene family (PAX2 and/or PAX8) in NAs may be helpful in the differential diagnosis of urothelial lesions and prostatic adenocarcinoma. NAs are most likely to be confused with clear cell adenocarcinoma, especially in small biopsy specimens. This is confounded by both lesions being frequently positive for PAX2, PAX8, and CK7 and not infrequently positive for p504S (α-methylacyl-CoA-racemase, AMACR) by immunohistochemistry. Recognition of its characteristic morphological patterns and awareness of its unusual architectural and cytological features are important in making the diagnosis of NA and distinguishing this lesion from its mimickers.

Is there a role for fatty acid synthase in the diagnosis of prostatic adenocarcinoma?: A comparison with AMACR

Our aim was to compare the usefulness of fatty acid synthase (FASn) with that of α-methylacyl coenzyme-A racemase (AMACR) in the diagnosis of prostatic adenocarcinoma. The expression of these 2 markers was compared in a tissue microarray containing 62 foci of benign glands and 36 foci of prostatic adenocarcinoma. Similar to AMACR, there was significantly higher FASn expression in adenocarcinoma compared with that in benign glands. The optimal accuracy rate and area under curve (AUC) by receiver operating characteristic analysis for FASn were not significantly different from those for AMACR (accuracy, 80% vs 87%; AUC, 0.942 vs 0.956; P for both, > .05). Moreover, in cases with coexistent malignant and benign glands on the same core, FASn could selectively distinguish a proportion of cases (17/21 [81%]) similar to using AMACR. We conclude that FASn may aid in the diagnosis of prostatic adenocarcinoma, at least to supplement AMACR as another positive marker of carcinoma and potentially increase diagnostic accuracy.

Diagnostic utility of α-methylacyl CoA racemase (P504S) & HMWCK in morphologically difficult prostate cancer

Background

To evaluate the diagnostic utility of alpha-methylacyl CoA racemase (P504S) & HMWCK (34beta E12) in morphologically difficult prostate cancer.

Methods

A total of 1034 cases were reviewed and divided into benign (585) malignant (399) and suspicious (50). Immunohistochemistry with HMWCK and AMACR was done on the 50 suspicious cases along with controls.

Results

Forty nine suspicious cases were resolved by using both markers where as 1 case was resolved by further support with CD68. The original diagnosis was changed in 15 of 50 (30%) suspicious cases from benign to malignant, one case from benign to high grade PIN and in one case from malignant to benign. Change of diagnosis was seen in 17 of 50 (34%) suspicious cases with a significant p value of 0.002. The overall diagnosis was changed in 17 of 1034 cases (1.64%) of prostatic disease (p < 0.001).

Conclusions

A combination of HMWCK and AMACR is of great value in combating the morphologically suspicious cases and significantly increasing the diagnostic accuracy in prostate cancer. Although, in this study the sensitivity and specificity of HMWCK and AMACR were high, yet it should be used with caution, keeping in mind all their pitfalls and limitations.

Nephrogenic adenoma: report of a case and review of morphologic mimics

Nephrogenic adenoma, also referred to as nephrogenic metaplasia, is an uncommon benign lesion of the urothelial tract, characterized by a circumscribed proliferation of tubules, cysts, and papillae lined by cells with low cuboidal to columnar epithelium. The diagnostic features that are useful in the recognition of this benign entity are the characteristic mixture of various architectural patterns, associated stromal edema and inflammation, hyaline sheath around tubules, eosinophilic colloidlike secretion within tubules, and lack of mitotic activity. Nephrogenic adenoma can be a significant diagnostic pitfall as certain histologic features, such as the presence of enlarged nuclei with prominent nucleoli, degenerative nuclear atypia, tiny tubules with blue mucin simulating signet ring cells, and focal invasion into superficial muscle, when taken out of context, can mimic malignancy. Herein, I report a case of nephrogenic adenoma with some worrisome histologic features and review the diagnostic criteria as well as pertinent morphologic malignant mimics of nephrogenic adenoma.

Cancer biomarker discovery: the entropic hallmark

Background

It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods.

Methodology/Principal Findings

Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer.

Conclusions/Significance

We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-througput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases.

S-100A1 is a reliable marker in distinguishing nephrogenic adenoma from prostatic adenocarcinoma

Nephrogenic adenoma is a benign lesion that may occur at any site of the genitourinary tract, usually in association with previous urothelial injuries. Although its pathogenesis is still debated, recent studies seem to confirm its derivation from renal tubular epithelium, rather than from a metaplastic process of urothelium. In addition to its uncertain origin, there can be diagnostic difficulty in distinguishing nephrogenic adenoma from prostatic adenocarcinoma, particularly with lesions arising in the prostatic urethra. So far, immunohistochemical stains are often needed to make such a distinction, and several markers have been proposed, often with controversial results. S100A1 is a calcium binding protein that has been recently reported to be expressed in renal tubular cells and in a subset of renal cell neoplasms. Alpha-methylacyl-CoA racemase (AMACR), a recently identified prostate cancer marker, has also been found to be expressed in renal tubules and in some renal epithelial neoplasms. In this study, we investigated the expression of S100A1 and AMACR in 18 nephrogenic adenomas and in 100 prostatic adenocarcinomas. A strong and distinct cytoplasmic or nucleocytoplasmic staining of S100A1 was found in 17 out of 18 cases of nephrogenic adenoma (94%), but never in prostatic adenocarcinoma. In contrast, AMACR expression was detected in 14 of 18 nephrogenic adenomas (78%) and in 96 of 100 prostatic adenocarcinomas (96%). We conclude that (1) S100A1 is a specific and sensitive immunohistochemical marker to differentiate nephrogenic adenoma from prostatic adenocarcinoma; (2) AMACR immunostaining does not seem to be a useful marker in distinguishing between these 2 lesions; (3) given that both S100A1 and AMACR have been reported to be expressed in renal tubular cells and in a subset of renal cell neoplasms, our findings confirm the histogenetic relationship between nephrogenic adenoma and renal tubular epithelium.

Clear cell adenocarcinoma of the bladder and urethra: cases diffusely mimicking nephrogenic adenoma

Although clear cell adenocarcinoma have been described focally mimicking nephrogenic adenoma, we have identified a subset of clear cell adenocarcinoma that diffusely resembles nephrogenic adenoma (nephrogenic adenoma-like clear cell adenocarcinoma). Twelve classic clear cell adenocarcinomas of the bladder and urethra and 7 nephrogenic adenoma-like clear cell adenocarcinomas were compared to 10 nephrogenic adenomas. Classic clear cell adenocarcinomas and nephrogenic adenoma-like clear cell adenocarcinomas comprised 4 men and 15 women. The following features were seen in classic clear cell adenocarcinomas: nephrogenic adenoma-like clear cell adenocarcinomas: predominantly solid pattern (7/12:0/7), marked nuclear pleomorphism (7/12:1/7), prominent nucleoli (5/12:1/7), clear cytoplasm in 50% or greater of tumor (7/12:0/7), and necrosis (8/12:3/7), although the necrosis in nephrogenic adenoma-like clear cell adenocarcinomas was often focal and intraluminal. Both patterns of clear cell adenocarcinomas showed prominent hobnail features, although more pronounced in nephrogenic adenoma-like clear cell adenocarcinomas. Muscularis propria invasion was seen in 5 of 9 classic clear cell adenocarcinomas and 6 of 6 nephrogenic adenoma-like clear cell adenocarcinomas, where evaluable. Classic clear cell adenocarcinoma was associated with urothelial carcinoma (n = 2) and endometriosis (n = 1). The Ki-67 rate in clear cell adenocarcinomas ranged from 10% to 80% compared with 0% to 5% in nephrogenic adenoma. The following antibodies were not helpful in distinguishing nephrogenic adenoma-like clear cell adenocarcinoma from nephrogenic adenoma: CD10, estrogen receptor, p63, high-molecular-weight cytokeratin, and alpha-methylacyl coenzyme-A racemase. PAX2 expression was more frequent in nephrogenic adenoma (89%) compared to both patterns of clear cell adenocarcinoma (29%-32%). The key features discriminating between nephrogenic adenoma-like clear cell adenocarcinoma and nephrogenic adenoma include occasional clear cells, more prominent pleomorphism especially hyperchromatic enlarged nuclei, and extensive muscular invasion. Presence of mitoses and a high rate of Ki-67 expression in lesions resembling nephrogenic adenoma require clinical correlation, close follow-up, and repeat biopsy with more extensive sampling.

Evaluation of routine application of P504S, 34betaE12 and p63 immunostaining on 250 prostate needle biopsy specimens

BACKGROUND

We aimed to determine whether a standard P504S, 34betaE12 and p63 immunostaining of prostate core needle biopsy specimens can optimize diagnostic accuracy of conventional staining methods.

MATERIALS AND METHODS

The staining properties of all three antibodies were evaluated on 250 prostate biopsies formerly diagnosed as benign.

RESULTS

Lack of basal cell staining in more than three glands for 34betaE12 and p63 occurred in 41 (27.5%) and 9 (6%) respective cases from the General Hospital pool. Respective figures from the Uropathology department specimens were 18 (18%) for 34betaE12 and 8 (8%) for p63. With the aid of P504S positivity, a case of prostate cancer as well as another of atypical small acinar proliferation was discovered.

CONCLUSION

Despite its potential for important aid in accurate diagnosis, standard application of immunohistochemistry in prostate biopsy is not justified and should be reserved for equivocal cases where conventional pathology fails to be conclusive.

Tumor-like lesions of the urinary bladder

Tumor-like lesions of the urinary bladder are reviewed emphasizing those that are most diagnostically challenging for the pathologist and may result in serious errors in patient care if misinterpreted. The first category considered, pseudocarcinomatous proliferations, represents an area of bladder pathology only recently appreciated as being particularly treacherous because of the extent to which irregular islands of benign epithelial cells may seemingly penetrate the lamina propria and cause confusion with carcinoma. Somewhat orderly proliferations of this type have been known for years, von Brunn's nests, and are rarely a challenge for the experienced, but proliferations of an irregular nature such as may be seen most often as a result of prior radiation therapy, but sometimes due to chemotherapy or even ischemia, represent a challenging interpretation. The clinical history may be very important in arriving at the correct diagnosis as is the appreciation that the morphology, although architecturally problematic, is different from that of any of the familiar patterns of invasive carcinoma. Florid epithelial proliferations in fibroepithelial polyps are also briefly noted. Within the category of glandular proliferations, emphasis is placed on the wide spectrum of morphology of nephrogenic adenoma including its pseudoinfiltrative pattern and occasional propensity for tiny tubules to be misconstrued as signet-ring cells. The spectrum of müllerian glandular lesions including the relatively recently described mucinous variant, endocervicosis, is reviewed. The reactive papillary proliferation, papillary-polypoid cystitis, is then discussed. This entity has long been known but has recently been re-emphasized. Other non-neoplastic papillary lesions include florid papillary forms of nephrogenic adenoma. The past 25 years has seen a great expansion of knowledge concerning non-neoplastic spindle cell proliferations, including those related to a prior procedure, the postoperative spindle cell nodule and those without such a history, variously designated inflammatory pseudotumor, pseudosarcomatous myofibroblastic proliferation, or even other terms. The morphologic spectrum is explored and it is recommended that the two categories be retained.

Utility of diagnostic and prognostic markers in urothelial carcinoma of the bladder

Urothelial carcinoma (UCC) of the bladder demonstrates diverse morphologic features, often leading to diagnostic challenges in the discrimination between UCC and benign mimickers of neoplasia, and between primary UCC and secondary neoplasms involving the bladder. In situ lesions also provide diagnostic difficulty in some instances, most prominently in the distinction between normal, reactive urothelium and flat urothelial carcinoma in situ. The use of ancillary techniques, including panels of immunohistochemical markers, in distinguishing these entities has aided not only in the diagnosis of UCC, but has also provided insight into the molecular pathogenesis and prognostic value of numerous molecular pathways in UCC. This review focuses on some of the more commonly encountered biomarkers in UCC and their role in addressing key diagnostic and prognostic issues in this disease process.

Benign Diseases of the Bladder

Benign diseases of the bladder often present diagnostic challenges to practicing pathologists due to their diverse nature and ability to mimic a variety of epithelial or mesenchymal neoplasms. Categories of benign bladder disease include infectious cystitis, noninfectious cystitis, reactive proliferative processes, and benign processes that secondarily involve the bladder. An understanding of the key clinical and morphologic features of these lesions and the useful ancillary techniques specific for these entities is critical to the correct diagnosis of these lesions. This article reviews the key features of these benign bladder diseases and highlights methods to distinguish these lesions from other benign and malignant processes involving the bladder.

Benign Mimickers of Prostate Adenocarcinoma on Needle Biopsy and Transurethral Resection

Prostate needle biopsy currently is the gold standard method for the diagnosis, management, and prognosis of prostate cancer. Obtaining an accurate diagnosis is crucial for pursuing proper patient management. This article discusses histologic mimickers of prostate carcinoma highlighting microscopic features that are helpful to reach a correct diagnosis and emphasizing potential diagnostic pitfalls.

Divergent differentiation in urothelial carcinoma and other bladder cancer subtypes with selected mimics

Conventional urothelial carcinoma accounts for most carcinomas of the urinary tract lining. However, neoplastic urothelium has the capacity to demonstrate enormous plasticity. A variety of unusual architectural patterns of urothelial carcinoma, such as the nested, microcystic and inverted variants, can be mistaken for reactive processes or benign tumours. Others such as the micropapillary, plasmacytoid and discohesive variants, can mimic metastatic tumour from other sites. The micropapillary variant in particular is more aggressive. In addition, urothelial carcinoma has a propensity to demonstrate divergent differentiation with glandular, squamous, small cell neuroendocrine, lymphoepithelioma-like, sarcomatoid or other elements. Pure squamous carcinoma or adenocarcinoma (the latter in particular) can be difficult to distinguish from contiguous or metastatic spread. Some variants have prognostic and potential therapeutic implications. Molecular genetic evidence has emerged recently supporting a close relationship between urothelial carcinoma and various divergent elements. Sarcomatoid carcinoma and its differential diagnosis with other spindle cell lesions of urinary tract will be covered in a separate review.

Clear cell adenocarcinoma of urinary bladder and urethra: another urinary tract lesion immunoreactive for P504S

CONTEXT

Clear cell carcinoma of the urinary bladder/ urethra is a rare tumor histologically resembling the neoplasms in the female genital tract. Adequate characterization of this tumor has been hampered by its rarity. alpha-Methylacyl-CoA racemase (AMACR)/P504S has been reported to be positive in prostatic adenocarcinoma, papillary renal cell carcinoma, and gastrointestinal neoplasmas; however, it has never been studied in clear cell carcinoma of the lower urinary tract.

OBJECTIVE

To investigate the immunohistochemical staining profile in 4 primary clear cell carcinomas of the urinary tract, including P504S, which has not been previously evaluated in these tumors.

DESIGN

Four cases of clear cell adenocarcinoma were retrieved from our archives: 2 cases from the urinary bladder (one each from a man and a woman) and 2 cases from the urethra (both from women, 1 in a diverticulum). Immunohistochemistry performed on the cases were P504S, K903, cytokeratin (CK) 7, CK20, CA 125, and p63.

RESULTS

We found that clear cell carcinomas had a distinct immunoreactive profile: strongly positive for P504S, K903, and CK7, and negative for p63. Two cases were also positive for CA 125 and CK20.

CONCLUSION

The immunohistochemical profile of clear cell carcinomas shares some similarity to conventional urothelial carcinoma; however, it deviates from those tumors in being positive for P504S and negative for p63. This staining profile may suggest a nonurothelial origin for these tumors, may serve as a useful tool in the differential diagnosis of this tumor, and may reflect its etiology. Because similar expression of P504S is also seen in nephrogenic adenomas, this marker should not be used to differentiate nephrogenic adenomas from clear cell adenocarcinomas.

Best practice in diagnostic immunohistochemistry: prostate carcinoma and its mimics in needle core biopsies

CONTEXT

The unrelenting challenge encountered when differentiating limited-volume prostate carcinoma and sometimes subtle variants from its many morphologic mimics has increased the use of ancillary immunohistochemistry in routine prostate needle biopsies. The availability of prostate cancer-associated and basal cell-associated markers has been an invaluable addition to diagnostic surgical pathology.

OBJECTIVE

To review commonly used immunohistochemical stains, including innovative combinations, for confirmation or differential diagnosis of prostate carcinoma, and to propose appropriately constructed panels using morphologic patterns in prostate needle biopsies.

DATA SOURCES

These best practices are based on our experience with routine and consultative case sign-outs and on a review of the published English-language literature from 1987 through 2008.

CONCLUSIONS

Basal cell-associated markers p63, high-molecular-weight cytokeratin 34 beta E12, cytokeratin 5/6 or a cocktail containing p63 and high-molecular-weight cytokeratin 34 beta E12 or cytokeratin 5/6 and prostate carcinoma-specific marker alpha-methylacyl coenzyme A (coA) racemase alone or in combination are useful adjuncts in confirming prostatic carcinoma that either lacks diagnostic, qualitative or quantitative features or that has an unusual morphologic pattern (eg, atrophic, pseudohyperplastic) or is in the setting of prior treatment. The combination of alpha-methylacyl coA racemase positivity with negative staining for basal cell-associated markers supports a malignant diagnosis in the appropriate morphologic context. Dual chromogen basal cell- associated markers (p63 [nuclear] and high-molecular-weight cytokeratin 34 beta E12/cytokeratin 5/6 [cytoplasmic]) and alpha-methylacyl coA racemase in an antibody cocktail provide greater sensitivity for the basal cell layer, easing evaluation and minimizing loss of representation of the focal area interest because the staining is performed on one slide. In the posttreatment setting, pancytokeratin facilitates detection of subtle-treated cancer cells. Prostate-specific antigen and prostatic acid phosphatase markers are helpful in excluding secondary malignancies involving the prostate, such as urothelial carcinoma, and occasionally in excluding nonprostatic benign mimickers, such as nephrogenic adenoma, mesonephric gland hyperplasia, and Cowper glands. There is no role for ordering immunohistochemistry prospectively in all cases of prostatic needle biopsies.

Expression of alpha-methylacyl-CoA racemase correlates with histopathologic grading in noninvasive bladder cancer

Alpha-methylacyl-CoA racemase (AMACR, p504S), an enzyme involved in cellular energy metabolism by the oxidation of branched-chain fatty acids, is a biomarker that is known to be overexpressed in prostatic and colorectal carcinoma as well as in papillary renal cell carcinoma. We aimed to correlate its immunohistochemically detected expression with histopathological grading in noninvasive bladder cancer in order to hint at a so far unknown role of AMACR in the pathobiology of this tumor entity. Therefore, a cohort of 163 patients (mean age 65.3 years) diagnosed with noninvasive bladder cancer was immunohistochemically investigated in terms of AMACR expression. There was variable positive AMACR staining in 52 (31.9%) of the cases investigated. All tumors were graded by three independent clinical histopathologists according to the 1973 World Health Organization (WHO) and the 1998 WHO/International Society of Urological Pathology (ISUP) system. We found a significant positive correlation between AMACR expression and higher tumor grades using both histopathologic grading schemes. These novel findings clearly allow including high-grade noninvasive bladder carcinomas in the group of AMACR-positive neoplasms and might reflect a so far unknown role of AMACR racemase in the pathobiology and tumor cell energy metabolism of the latter tumor entity.

Histogenesis of clear cell adenocarcinoma in the urinary tract: evidence of urothelial origin

PURPOSE

Clear cell adenocarcinoma in the urinary tract is a rare entity with an appearance resembling its counterpart in the female genital tract. Although several theories have been proposed about its origin, its exact histogenesis has remained uncertain.

EXPERIMENTAL DESIGN

We integrated molecular genetic evaluation by fluorescence in situ hybridization and X-chromosome inactivation with conventional morphologic and immunohistochemical analyses in 12 patients with clear cell adenocarcinomas in the urinary tract.

RESULTS

Concurrent urothelial carcinoma or urothelial carcinoma in situ was present in six cases (50%) and foci of cystitis glandularis were observed in four cases (33%). Neither intestinal metaplasia nor Müllerian component was identified in any case. Cytoplasmic expression of alpha-methylacyl-CoA racemase was demonstrable in 10 of 12 tumors (83%). Moderate to diffuse immunostaining for cytokeratin 7 was identified in all 12 tumors (100%), whereas only 3 of 12 (25%) tumors showed positive immunostaining for cytokeratin 20. Focal uroplakin III staining was seen in 6 of 12 tumors (50%). In five cases (42%), focal to moderate CD10 immunoreactivity was observed. Immunostains for OCT4 and CDX2 were completely negative in all tumors. In UroVysion fluorescence in situ hybridization assays, all tumors displayed chromosomal alterations similar to those commonly found in urothelial carcinoma. Identical patterns of nonrandom X-chromosome inactivation in concurrent clear cell adenocarcinoma and urothelial neoplasia were identified in two informative female cases.

CONCLUSIONS

Our findings support an urothelial origin for most clear cell adenocarcinomas of the urinary tract, despite their morphologic resemblance to certain Müllerian-derived tumors of the female genital tract.

Pitfalls in the diagnosis of prostatic cancer: retrospective review of 1791 cases with clinical outcome

AIMS

To assess the possible reasons for error in the diagnosis of prostatic cancer with available follow-up data.

METHOD AND RESULTS

A cohort of 1791 cases of prostatic cancer diagnosed in the UK between 1990 and 1996 was examined. All cases were clinically localized at presentation, treated by non-curative methods and detailed follow-up was available. A panel of genitourinary pathologists reviewed the pathology of all cases. One hundred and thirty-three (7.5%) of cases were reassigned to a non-malignant diagnosis. Where possible, reasons for the initial diagnosis were given. These included severe atrophy, inflammatory induced atypia, sclerosing adenosis, atypical adenomatous hyperplasia and basal cell hyperplasia. Follow-up of these patients showed an extremely low death rate from prostatic cancer: lower than that for the Gleason combined score of five or less tumours diagnosed in this series.

CONCLUSIONS

Many morphological entities potentially mimic prostatic cancer and may be responsible for misdiagnosis in routine specimens. Continuing education in prostatic morphology and immunohistochemistry may have helped reduce this error rate.

Fibromyxoid Nephrogenic Adenoma: A Newly Recognized Variant Mimicking Mucinous Adenocarcinoma

Nephrogenic adenomas demonstrate a variety of morphologic patterns that may occasionally be confused with malignant processes, including urothelial and prostatic carcinoma. In this series, we describe 8 cases of nephrogenic adenoma that contain an admixture of the classic tubular form of nephrogenic adenoma and an unusual spindled and fibromyxoid form of nephrogenic adenoma that closely mimics infiltrating carcinoma. In all cases, the classic tubular form of nephrogenic adenoma composed only a small proportion of the lesion, whereas the remainder consisted of compressed spindled cells within a fibromyxoid background, with only rare tubular and cordlike structures. On close examination, minimal nuclear atypia was identified in 2 cases, which included small, pinpoint nucleoli, and nuclear pseudoinclusions. All 8 patients were elderly men who had a prior or concurrent history of acinar prostate cancer (n=4), combined acinar prostate and urothelial carcinoma (n=1), urothelial-type adenocarcinoma of the prostate (n=1), bladder urothelial carcinoma (n=1), or no prior reported prostatic or urothelial abnormalities (n=1). Five patients received prior treatment with radiotherapy, 1 patient received intravesical mitomycin-C, and 1 also received bacillus Calmette-Guerin. The epithelial component of the lesions was positive in all cases for pancytokeratin (AE1/3) and racemase and demonstrated a variable cuff of type IV collagen surrounding the tubules. PAX-2 was positive with variable extent of labeling. Immunostains for prostate-specific antigen were negative. Histochemical stains identified some of the background matrix as mucin, with intense staining for periodic acid-Schiff and focal staining for mucicarmine. Stains for reticulin and amyloid (Congo red stain) and immunohistochemistry for Tamm-Horsfall protein were negative. This case series is the first report of a fibromyxoid subtype of nephrogenic adenoma. Awareness of this entity and the use of ancillary techniques can aid in the diagnosis of this unusual form of nephrogenic adenoma.

Diagnosis of adenocarcinoma in prostate needle biopsy tissue

Prostate cancer is a major public health problem throughout the developed world. For patients with clinically localised prostate cancer, the diagnosis is typically established by histopathological examination of prostate needle biopsy samples. Major and minor criteria are used to establish the diagnosis, based on the microscopic appearance of slides stained using haematoxylin and eosin. Major criteria include an infiltrative glandular growth pattern, an absence of basal cells and nuclear atypia in the form of nucleomegaly and nucleolomegaly. In difficult cases, basal cell absence may be confirmed by immunohistochemical stains for high-molecular-weight cytokeratins (marked with antibody 34betaE12) or p63, which are basal cell markers. Minor criteria include intraluminal wispy blue mucin, pink amorphous secretions, mitotic figures, intraluminal crystalloids, adjacent high-grade prostatic intraepithelial neoplasia, amphophilic cytoplasm and nuclear hyperchromasia. Another useful diagnostic marker detectable by immunohistochemistry is alpha-methylacyl coenzyme A racemase (AMACR), an enzyme selectively expressed in neoplastic glandular epithelium. Cocktails of antibodies directed against basal cell markers and AMACR are particularly useful in evaluating small foci of atypical glands, and in substantiating a diagnosis of a minimal adenocarcinoma. Reporting of adenocarcinoma in needle biopsy specimens should always include the Gleason grade and measures of tumour extent in the needle core tissue. Measures of tumour extent are (1) number of cores positive for cancer in the number of cores examined, (2) percentage of needle core tissue affected by carcinoma and (3) linear millimetres of carcinoma present.

α-methylacyl-CoA racemase (P504S)/34βE12/p63 triple cocktail stain in prostatic adenocarcinoma after hormonal therapy

Alpha-methylacyl-CoA racemase (AMACR) has recently been shown to be a highly sensitive marker for the diagnosis of prostate cancer. However, there is limited information concerning its utility as a marker for prostate carcinoma after hormonal therapy. Our current investigation was conducted to evaluate the expression of AMACR in patients with prostate carcinoma after hormonal therapy and assess its diagnostic utility in combination with p63 and high molecular weight cytokeratin (34betaE12) staining. Prostate tissues from 49 patients who had been treated with hormonal therapy were immunohistochemically analyzed for AMACR, 34betaE12, and p63 expression by a triple antibody cocktail stain. The staining intensities and the percentages of positively staining tumor cells were recorded. The correlations between AMACR expression and metastatic status, associated hormonal therapy regimens, and the extent of hormone therapy effect were analyzed. All malignant acini were completely negative for both basal cell markers (34betaE12 and p63). Tumor cells failed to demonstrate expression of AMACR in 14 (29%) of 49 cases. In the remaining 35 cases (71%), positive immunostaining for AMACR was noted, but with variable intensities and percentages of cells stained. Positive staining for AMACR in benign glands was not seen in any case. In all cases, basal cells were strongly stained by p63 in benign acini with a mean positive percentage of 96%. Similarly, basal cells in benign acini displayed moderate staining intensities for 34betaE12 in 3 (7%) of 41 cases and strong immunostaining for this marker in the remaining 38 cases (93%); the mean percentage of positive cells was 92%. alpha-methylacyl-CoA racemase expression may be substantially diminished or entirely lost in prostate carcinoma after hormonal therapy. This variation in AMACR expression does not correlate with the metastatic status, the modality of hormonal therapy, or the extent of therapy-related effect. It is important that pathologists be aware that some hormonally treated prostate carcinomas do not express AMACR, and that immunostaining in such cases must be interpreted with caution. A triple cocktail stain using AMACR, 34betaE12, and p63 can be helpful in evaluating prostate specimens for the presence of residual or recurrent carcinoma after hormonal therapy for cancer.

Nephrogenic adenoma: an update on an innocuous but troublesome entity

Nephrogenic adenoma (NA) is a rare benign lesion of the urothelial tract that is typically preceded by some form of genitourinary insult. The pathogenesis of NA is not entirely clear. Although generally presumed to be a metaplastic process of the urothelium, recent evidence suggests that NA may in fact be derived from detached renal tubular cells implanting along the urothelial tract in previously injured areas, at least in cases associated with a kidney transplant. On light microscopy, NA shows a variety of patterns, including tubulocystic, papillary, and much less frequently solid, that often coexist. Recognition of its characteristic patterns, and awareness of its unusual architectural and cytologic features, is key to making the diagnosis of NA and distinguishing this lesion from malignant neoplasms occurring at the same sites, in particular, clear cell carcinoma, nested or microcystic variants of urothelial carcinoma and prostatic adenocarcinoma. Although straightforward in most cases, the correct diagnosis may be difficult to make on limited tissue samples. A number of immunohistochemical markers have been studied in an attempt to characterize NA; however, to date there is no specific immunohistochemical profile to distinguish this lesion from its malignant mimickers, although PAX2, a new marker, may prove to be helpful in this regard. Clinicopathologic correlation with careful attention to morphology remains the pillar in establishing the correct diagnosis.

The prostate-specific G-protein coupled receptors PSGR and PSGR2 are prostate cancer biomarkers that are complementary to alpha-methylacyl-CoA racemase

BACKGROUND

Immunohistochemistry (IHC) to detect alpha-methylacyl-CoA racemase (AMACR) expression can be useful in the diagnosis of small foci of prostate cancer on needle biopsy specimens, although it still has limitations in terms of both sensitivity and specificity. We have previously described the increased expression of two prostate-specific G-protein coupled receptors (PSGR and PSGR2) in human prostate cancer. To examine their potential usefulness as cancer biomarkers, we have evaluated their expression relative to AMACR in prostate cancer tissues.

METHODS

Expression of PSGR, PSGR2, and AMACR were examined by quantitative reverse-transcriptase PCR in mRNAs from benign prostate and prostate cancer tissues. Expression of PSGR2 and AMACR was also examined by in situ hybridization using a prostate cancer tissue microarray.

RESULTS

By in situ hybridization, 24 of 40 prostate cancer cases showed concordant expression of PSGR2 and AMACR. However, in 16 cases there was significant discordance between expression levels of these two markers. By quantitative RT-PCR all three markers were substantially increased in cancer, with AMACR the most overexpressed (30-fold), followed by PSGR2 (13-fold) and PSGR (10-fold). AMACR was the best single marker of prostate cancer but in 7 of the 59 total cases the expression of AMACR was not significantly elevated while PSGR and/or PSGR2 were substantially elevated.

CONCLUSION

All three biomarkers are increased in prostate cancer but their expression is not completely concordant. There is a subset of cases in which analysis of expression of PSGR and/or PSGR2, in addition to AMACR, would be diagnostically useful.

PAX2: a reliable marker for nephrogenic adenoma

Nephrogenic adenoma is a rare lesion of the urinary tract. The diagnosis usually is straightforward when characteristic microscopic and clinical findings are present, and the entity is familiar. However, misdiagnosis, in particular of adenocarcinoma of the prostate gland, may occur. Immunohistochemical stains often are needed to make such a distinction, but currently available markers offered only partial help. It recently was demonstrated that nephrogenic adenoma in renal transplant patients originated from the renal tubular epithelium. This newly proved, but long sought information may be helpful in the differential diagnosis of nephrogenic adenoma. In this study, we investigated the expression of a renal transcription factor, PAX2, in 39 nonrenal transplant-related nephrogenic adenomas, 100 adenocarcinomas of the prostate gland, and 47 urothelial carcinomas of the urinary tract. A strong and distinct nuclear staining of PAX2 was found in all 39 cases of nephrogenic adenoma (100%), but not in normal prostate tissue, normal urothelium, adenocarcinomas of the prostate gland, and invasive urothelial carcinomas. Focal CD10 was detected in six of 13 nephrogenic adenomas in the superficial papillary component and in normal prostate epithelium, normal urothelium, lymphocytes, adenocarcinoma of the prostate gland, and urothelial carcinoma. There was no uroplakins detected in nephrogenic adenoma. Therefore, these findings are suggesting that nephrogenic adenoma in nonrenal transplant patients may also arise from the renal epithelium, as did the comparable lesions after transplantation. PAX2 is a specific and sensitive immunohistochemical marker in identification and differential diagnosis of nephrogenic adenoma.

Comparison of monoclonal antibody (P504S) and polyclonal antibody to alpha methylacyl-CoA racemase (AMACR) in the work-up of prostate cancer

AIM

Studies using a monoclonal (P504S) and a polyclonal antibody (p-AMACR) to alpha-methylacyl-CoA racemase (AMACR) have shown variable expression in prostate cancer (PCa). The goal is to compare the sensitivity of both antibodies in PCa and evaluate their utility in the work-up of atypical prostate needle biopsies (NBXs).

METHODS AND RESULTS

A tissue microarray (TMA) with 248 samples of benign prostate, high-grade prostatic intraepithelial neoplasia (HGPIN) and PCa samples, 20 NBXs with minute PCa and 32 NBXs with 'atypical' foci were stained with P504S and p-AMACR. Ninety percent of PCa (76/76 TMA, 16/20 NBXs) showed predominantly strong p-AMACR expression while 87% (65/69 TMA, 16/20 NBXs) showed variable P504S expression (sensitivity 90% versus 87%, P = 0.10). In HGPIN, P504S and p-AMACR were positive in 77% and 91% of samples, respectively. In the 'atypical' NBXs group, 53% were classified as PCa, 12% benign and 35% atypical, suspicious for PCa, after review of the basal marker. Of atypical, suspicious for PCa, P504S/p-AMACR helped convert the diagnosis to PCa in 5/11 (45%) cases, where, despite negative basal cell markers, morphology was less than optimal.

CONCLUSIONS

Differences between P504S and p-AMACR appear marginal and clinically insignificant. AMACR is negative in a subset of unequivocal minute PCa with both antibodies. However, when utilized in proper context, AMACR may offer significant advantage in converting an 'atypical' diagnosis to PCa where morphology and basal markers are less than optimal in resolving the diagnosis.

[Differential diagnosis of prostate cancer: impact of pattern analysis and immunohistochemistry]

Prostate cancer offers a wide range of growth patterns depicted in the classical Gleason diagram. For each Gleason pattern exist a number of benign and malignant mimickers that can simulate prostatic adenocarcinoma. In the present review, the use of immunohistochemical markers is discussed with emphasis to a pattern-based approach to differential diagnosis in prostate pathology. Basal cell markers (34betaE12 and P63) are very useful to analyze histo-architectural features of small and large glandular lesions. AMACR (P504 s) is helpful not only in identifying small amount of cancer in needle biopsies but also in the diagnosis of high grade prostatic intra epithelial neoplasia (HGPIN). A number of lesions which may be confused with small acinar adenocarcinoma (Cowper's gland, nephrogenic metaplasia, mesonephric glands) and poorly differentiated prostate cancer (urothelial neoplasia, mucinous colon cancer and other metastatic lesions) lacks convincing PSA immunoreactivity. Basal cell markers and the nuclear androgen receptors are important markers to differentiate Gleason grade 5 A und 5 B patterns from prostatic involvement by transitional cell carcinoma. Finally, a selected panel of markers is useful to classify prostatic stromal lesions. In each case, immunohistochemical findings should be interpreted in context with the various patterns on routine microscopy.

Diagnostic utility of immunohistochemistry in morphologically difficult prostate cancer: review of current literature

Varma M & Jasani B (2005) Histopathology47, 1-16 Diagnostic utility of immunohistochemistry in morphologically difficult prostate cancer: review of current literatureImmunohistochemistry is widely used to distinguish prostate cancer from benign mimics and to establish the prostatic origin of poorly differentiated carcinoma. We critically review the recent advances in prostate cancer immunohistochemistry, including the introduction of newer basal cell markers such as p63 and the discovery of the overexpression of alpha-methylacyl coenzyme A racemase (AMACR) in prostate cancer. The description of newer urothelial markers to aid the distinction of prostate cancer from urothelial carcinoma is also presented together with refinements in the quality control of PSA and PSAP immunostaining. Although AMACR is a useful immunohistochemical marker for prostate cancer, it has significant limitations. These limitations are discussed and the need for interpreting AMACR immunoreactivity in the appropriate morphological context and in conjunction with basal call markers is emphasized. We also describe the utility of an immunohistochemical panel composed of PSA, PSAP and high molecular weight cytokeratin for distinguishing poorly differentiated prostate cancer from high-grade urothelial carcinoma. A morphological differential diagnosis based selection of immunohistochemical markers is highlighted as a novel approach in the diagnosis of prostate cancer in routine surgical pathology practice.